1. Field of the Invention
The present invention relates to a liquid droplet jetting apparatus including a jetting head unit which jets liquid droplets, in particular, to a structure capable of preventing minute liquid droplets (mist), which are generated when the liquid droplets are jetted from nozzles, from entering a head holder including the jetting head unit.
2. Description of the Related Art
In a liquid droplet jetting apparatus, for example, an ink-jet recording apparatus described in US Patent Publication No. 2006087532 (corresponding to Japanese Patent Application Laid-open No. 2006-123246), a jetting head unit (recording head) which jets liquid droplets (ink droplets) is provided on a side of a lower surface of a box-shaped head holder. An electric circuit board is disposed on an upper side of the head holder, and a cover provided on a side of an upper surface of the electric circuit board covers an opening of the head holder.
When the ink droplets are jetted from a nozzle of the recording head, not only main ink droplets which form dots on a recording paper are jetted, but also minute ink droplets in mist form, that is, ink mist, are generated. This ink mist can pass through even a narrow gap. Therefore, if the ink mist enters from a gap between the aforesaid cover and opening of the head holder and adheres to a conductive portion of the electric circuit board, ion migration occurs, which may possibly cause electric short circuit.
To avoid this phenomenon, in the ink-jet recording apparatus described in US Patent Publication No. 2006087532, a shielding member to block the entrance of the ink mist is interposed in a gap which is formed between a peripheral edge surrounding an electric circuit formation area in the electric circuit board and a rear surface of the cover.
To meet a recent demand for higher recording speed and higher density of a recording apparatus, the number of nozzles jetting liquid has been increasing. Therefore, a size of a jetting head becomes large and a size of a head holder also becomes large. Accordingly, when the cover is provided as in the ink-jet recording apparatus described in US Patent Publication No. 2006087532, the cover has to be made larger, and a carriage having these components thereon accordingly becomes heavier. A carriage motor also has to be made larger so that the carriage with the increased weight can move at a higher speed (higher recording speed). Thus, the whole recording apparatus becomes larger and heavier, which causes a problem of an increase in manufacturing cost.